A randomized, double-blind clinical trial has been designed that will test the efficacy and safety of fluoride therapy in the prevention of further vertebral compression fractures in white postmenopausal females (the segment of the population at greatest risk) who have already sustained at least one vertebral fracture as a result of osteoporosis. The trial will also determine prospectively the fracture incidence of the population at risk prior to the initiation of fluoride therapy. We shall attempt to determine those indices of skeletal homeostasis that might predict the long-term response to fluoride therapy either before therapy is initiated or within the first three to six months after starting therapy. The effect of fluoride therapy on the morbidity from vertebral compression fractures will also be determined. We shall directly compare four methods of detecting vertebral fractures (serial measurement of vertical height, clinical episodes of acute back pain, measurements of vertebral body dimensions on standard radiographs of the spine in the lateral projection, and bone scan) to determine which is the most sensitive, safe and cost effective method of accurately detecting new fractures.